1. Field of the Invention
The present invention relates to a wastewater treatment ship to perform purification treatment on wastewater such as oil bearing wastewater collected from ships, spilled oil in the sea by accidents/mishaps, and domestic wastewater.
2. Description of the Related Art
Oil bearing wastewater including bilge water, tank washing water, polishing and cleaning water for a hull and the like are accumulated in a bottom of a ship. Conventionally, wastewater of this kind, after being stored temporarily in a tanker in a ship, has been collected from the ship by a wastewater collecting ship or wastewater collecting vehicle and conveyed to a land-based purification treatment facility.
However, the steps of collecting oil bearing wastewater from the temporary storing tank require much costs, time, and labors.
To solve these problems, the inventor of the present invention has disclosed, in Japanese Patent No. 4243603, an oil bearing wastewater treatment ship equipped with a waste oil treatment mechanism, which is disposed in an upper and inner portion of a hull being able to navigate by being towed or by being self-propelled, capable of carrying out purification treatment of a large amount of oil bearing wastewater.
The wastewater treatment mechanism has a raw wastewater housing tank to house collected oil bearing wastewater (raw wastewater), a purifying means for removing oil from raw wastewater, a purified water housing tank to house purified water (clean water) dischargeable in the sea and a waste oil housing tank to house oil removed from the raw wastewater as waste oil.
That is, in a oil bearing wastewater treatment ship disclosed in Japanese Patent No. 4243603, oil bearing wastewater and the like produced in other ship are collected to perform oil separating treatment on the site and the purified water can be discharged in the sea.
Therefore, unlike in the conventional case, treatment of collected oil bearing wastewater by a land-based purification treatment facility is not required, whereby costs and operating hours can be reduced.
In the case of a ship, besides the oil bearing wastewater, domestic wastewater produced by personnel aboard (including human waste) is discharged. In the past, the domestic wastewater was thrown away in the sea in a untreated state or after specified treatment, however, in recent years, proper treatment before discharging in the sea in accordance with regulations has been required.
To solve this problem, the inventor of the present invention disclosed, in Japanese Patent Application Laid-open No. 2009-45549, a domestic wastewater treatment ship equipped with a purification treatment mechanism capable of treating a large amount of domestic wastewater which is disposed in the upper and inner portions of a hull being able to be towed. The purification treatment mechanism has a collecting tank to house collected domestic wastewater (raw wastewater), a plurality of treatment tanks such as a stirring tank to perform purification treatment on the raw wastewater, and a tank to house purified water dischargeable in the sea.
That is, in the domestic wastewater treatment ship disclosed in the Japanese Patent Application laid-open No. 2009-45549, domestic wastewater can be collected from other ships and collected domestic wastewater can be purified and treated on the site and purified water can be discharged in the sea.
In the treatment ships disclosed in the Japanese Patent No. 4243603 and Japanese Patent Application laid-open No. 2009-45549, wastewater, after being purified to a specified level, is discharged in the sea and, therefore, purified water cannot be effectively used in a ship.
To solve this problem, the present inventor undertook thorough research to effectively reuse wastewater having undergone purification treatment on the sea. More specifically, a large amount of polishing and cleaning for a tank and water for domestic use other than drinking water is needed by a ship and, therefore, extensive research was made as to whether or not a system to easily reuse wastewater having undergone purification and treatment on the sea for the application described above can be provided.
Moreover, in the case of reusing purified water, a tank that can house a large amount of purified water is needed and tank weight changes greatly depending on amounts of purified water to be housed.
Therefore, in order to stabilize hull balance irrespective of an amount of wastewater to be treated, it is necessary to take, into consideration, procedures for purification treatment and location of each tank and thorough research was undertook on this regard accordingly.